Re: Where DAML+OIL deviates from the RDF-Schema spec.

On Sun, 4 Mar 2001, Tim Berners-Lee wrote:

> DAML is in my opinion right.  If a is a subclass of b and b of a mean
> that a and b are equivalent classes - this is not a bug.  You can't go
> peperring the underlying logical framework with exceptions just because
> in some cases a loop is formed by mistake. 

Tim, I agree that this isn't a bug. It is a feature, and you may or may
not like that feature. If you're an implementor features and bugs might be
difficult to distinguish. 

This has very little to do with underlying logical frameworks, but rather
with the semantics of "subPropertyOf" and "subClassOf" on the one hand,
and "samePropertyAs" and "sameClassAs", on the other. And in particular if
samePropertyAs is a subPropertyOf subPropertyOf ;)

I belong to those that feel any set of sub-properties to a certain
property X, should not contain any property which is equivalent with X. 
This is like the distinction between less than or equal to '<=', or just
less than '<'. You want subPropertyOf and subClassOf to be like '<='. But
I want them to be like '<', for reasons similar to those put forward by
Ian and DanBri, among others.

Your view is perfectly logical, as is that x1 <= x2 && x2 <= x1 implies
that x1 is equal to x2. However, I want subPropertyOf (X,Y) imply that Y
has a STRICTLY NARROWER semantics than X, and the same should go for
sameClassAs. 



Sigge

Received on Monday, 5 March 2001 02:40:19 UTC